package diedai;
public class CombineName {
    public static void main(String args[]) {
		int m = Integer.parseInt(args[0]);
		int n = Integer.parseInt(args[1]);
	    int sum=count(m,n);
	    if(sum==0) {
	        System.out.println("Error");
	    }
	    else {
	        System.out.println(sum);
	    }
   }
    public static int count(int m,int n) {
	    if(m<n||m<0||n<0){
		return 0;
 	    }
	    else if(n==m||n==0) {
		return 1;
	    }
	    else {
		return count(m-1,n-1)+count(m-1,n);
	    }
 	}
}
	    
		

